This invention relates to a windrow pickup attachment for use in conjunction with asphalt paving apparatus comprising an asphalt aggregate spreading unit and associated feed hopper.
In the building of asphalt roads, it is usual practice for dump trucks to deliver the asphalt aggregate paving material to the site and lay it in an elongated windrow along the longitudinal center line of the road section to be built. The windrow is substantially continuous and may be two to three feet deep and about eight feet wide.
While the aggregate still is soft, the paving apparatus straddles and moves along the length of the windrow. This apparatus broadly comprises a pickup unit which picks up the asphalt from the windrow, a feed hopper which receives the soft aggregate from the pickup unit, and a spreading unit which receives the aggregate from the feed hopper and spreads it laterally to the appropriate dimension, for example, about 15 feet. It is important that the asphalt thus spread be of uniform thickness and have a smooth, uniform surface.
Prior art patents which are of interest in connection with the picking up of asphalt and other materials and laying or spreading them on a surface include the following:
U.S. Pat. Nos. 1,258,299; 1,764,084; 1,987,398; 2,618,083; 2,627,680; 2,672,701; 3,103,754; 3,308,563; 3,479,775; 3,693,512; 3,885,332; 3,982,338; 4,011,023; 4,027,428.
The conventional prior art asphalt windrow pickup attachment is a heavy piece of apparatus mounted on caster wheels secured by a bracket to the front end of the paver equipment which accordingly pushes the attachment ahead of it. The front end of the attachment is provided with side guides which straddle the windrow. An endless flight conveyor delivers the paving material from the windrow rearwardly into the front portion of the paving apparatus. Conventionally, the side guides and conveyor are secured together permanently so that neither of them can move vertically without the other.
The primary problem attending the use of the prior art asphalt aggregate pickup attachments of this class resides in the fact that the conveyor flights pound down on the top of the windrow and are severely bent or broken. Downward pounding of the conveyor flights also tends to lift the entire attachment off the ground with its wheels or other supporting structure spinning about erratically. This imparts considerable vibration to the structure and affects adversely the quality of the pavement laid with the apparatus.
It is the primary purpose of the present invention to provide a windrow pickup attachment for asphalt paving apparatus which overcomes the foregoing problem and which is characterized by the following important advantages:
It picks up the windrow cleanly and efficiently.
During use, its pickup conveyor component is not subject to damage.
It places the aggregate properly in the hopper so that the hopper can be loaded to full capacity and unloaded efficiently and completely.
It is of high capacity.
It adapts to conventional asphalt paving equipment and may be mounted thereon without major modifications of equipment structure.
It is characterized by proper weight distribution, i.e. it has most of its weight forwardly so that it picks up the aggregate cleanly.
It is of relatively light weight and correspondingly low cost.
In its use it is not necessary to lift the asphalt beyond a minimum elevation.
It is safe in use.
It does not affect adversely the steering of the paving unit, i.e. does not draw the unit to one side or the other.
It requires only one motor to lift both its major components, i.e. both chute and chute conveyor.
It adjusts to windrows of varying height.
It is characterized by substantially vibrationless operation with resulting laying of asphalt pavement having a smooth, non-wavy surface.
We have discovered that the foregoing objects of the invention may be achieved by the provision of a windrow pickup attachment for hopper-equipped asphalt aggregate spreading units which, broadly considered, comprises an upwardly inclined, longitudinally arranged chute communicating with the hopper, pivotal mounting means mounting the rearward end of the chute adjacent the top of the hopper front wall at a relatively low elevation, and ground engaging means supporting the forward portion of the chute on the ground. A hydraulic cylinder or other drive means pivotally attached to the forward portion of the chute, reciprocates it between lowered working and raised transport positions.
An elongated, longitudinally extending chute conveyor frame overlies the hopper and the chute. Pivotal mounting means mount the rearward end of the frame adjacent the relatively elevated top of the hopper back wall.
An upwardly inclined chute conveyor is mounted on the conveyor frame in the chute, substantially aligned with the hopper and arranged for driving aggregate up the chute and into the hopper. Chute conveyor support means on the lower end of the chute conveyor frame support the same on the chute in sliding, supporting engagement therewith. Accordingly reciprocation of the drive means secures operative angular movement of both the chute and the chute conveyor, despite the fact that these two pivoting elements of the apparatus are not hinged on a common axis.